linux-kernel - Re: [PATCH] platform: set of_node in platform_device_register

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Message-ID: <yw1xef82wsqh.fsf@mansr.com>
Date:   Wed, 20 Feb 2019 12:26:46 +0000
From:   Måns Rullgård <mans@...sr.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform: set of_node in platform_device_register_full()

"Rafael J. Wysocki" <rafael@...nel.org> writes:

> On Wed, Feb 20, 2019 at 1:12 PM Måns Rullgård <mans@...sr.com> wrote:
>>
>> Johan Hovold <johan@...nel.org> writes:
>>
>> > On Wed, Feb 20, 2019 at 11:35:06AM +0000, Mans Rullgard wrote:
>> >> If the provided fwnode is an OF node, set dev.of_node as well.
>> >>
>> >> Some drivers are just shims that create extra "glue" devices with the
>> >> DT device as parent and have the real driver bind to these.  In these
>> >> cases, the glue device needs to get a reference to the original DT node
>> >> in order for the main driver to access properties and child nodes.
>> >>
>> >> For example, the sunxi-musb driver creates such a glue device using
>> >> platform_device_register_full().  Consequently, devices attached to
>> >> this USB interface don't get associated with DT nodes, if present,
>> >> the way they do with EHCI.
>> >>
>> >> This change will allow sunxi-musb and similar driver to easily
>> >> propagate the DT node to child devices as required.
>> >
>> > Just a drive-by comment, didn't look to closely at this patch, but this
>> > all sounds familiar.
>> >
>> > Note that if both platform devices are bound to drivers you may end up
>> > with some resources like pinctrl which are handled automatically by
>> > driver core at probe time to be requested twice (and failing the second
>> > time).
>> >
>> > Take a look at 4e75e1d7dac9 ("driver core: add helper to reuse a
>> > device-tree node"), which provides a means to avoid this, and
>> > 49484abd93ab ("USB: musb: dsps: propagate device-tree node").
>>
>> Thanks, and ugh.  So we should be setting the of_node_reused flag when
>> this is the case.  It's easy for the musb-dsps driver since it doesn't
>> use platform_device_register_full() and can do this before the
>> device_add() call.  How can we convey that this flag needs to be set?
>
> Through pdevinfo I guess?

Not without adding another field to it.  The most direct is of course to
simply add an of_node_reused flag there too and copy it over.  Would
that be OK, or is there a better way?

-- 
Måns Rullgård